Adhesive label sheets having at least one label and a liner sheet, in which the label is releasably adhered to the liner sheet by a pressure sensitive adhesive, are well known. The pressure sensitive adhesive on the back of the labels is usually, though not necessarily, of sufficient strength as to permanently adhere the label to an object to which the label is later affixed after the label has been peeled from the liner sheet and applied to the object. Such a pressure sensitive adhesive is generally referred to as a permanent pressure sensitive adhesive, as opposed to a releasable pressure sensitive adhesive. Even though the pressure sensitive adhesive is often of the permanent type, the labels can be easily removed from the liner because the liner, often referred to as the release liner, is covered with a non stick coating such as a thin layer of silicone. Labels and label sheets of this type are well known.
Labels of this sort can be manufactured and used in a variety of applications. One application for labels of this type is for use in labeling compact discs (CD's). International Publication WO 02/38371-A1, assigned to the assignee of the present invention, describes one such label sheet for CD's. The label sheet is of a standard size such as 8½×11 inches, or A4, for feeding through a standard printer attached to a personal computer such as a laser printer or ink jet printer. The facestock contains two CD labels and several CD jewel case spine labels die cut into the facestock so that they can be removed from the remainder of the label sheet when the user is ready to apply the CD label to a CD, or the spine label to a jewel case spine. Also die cut into the facestock sheet are the center holes or cutouts within the center of the CD labels. The facestock includes holding tabs or “no touch tabs” held to the CD, so that the user can hold the CD label while it is being positioned over the CD for application thereon without touching an adhesive surface. The holding tabs are typically removed from the CD label after the CD label has been placed onto the CD by tearing along perforations or cuts and ties formed in the facestock.
The liner also has various die cuts in it for different purposes. Those cuts include: cuts to allow the two halves of the label sheet to be separated for separate handling after printing; a crescent shaped cut at one each of the holding tabs to assist the user in grasping the tab and using it to peel the CD label from the label sheet; and small cross hairs and arcuate sections in the center hole sections of the CD labels for die alignment purposes when setting up the manufacturing equipment. The holding tab having the crescent shaped cut at its end so that the user can easily grasp it and use it to peel the CD label from the label sheet will be referred to as the peel tab. The various cuts in the facestock and the liner sheet are shown and/or described in WO 02/38371-A1.
Even though the die cuts defining the CD label and the center hole section may pass completely through the facestock, the two sections nevertheless sometimes remain stuck slightly together. This is because the pressure sensitive adhesive on the back of the label spreads and interacts with the pressure sensitive adhesive on the back of the center hole section, causing the two sections to stick together slightly at their edges along the die cut boundary. The sticking of the pressure sensitive adhesive on the back side of the two pieces thus tending to hold the two pieces together is sometimes referred to as cohesion. In contrast, the tendency of the facestock to stick to the liner due to the normal action of the pressure sensitive adhesive is usually referred to as adhesion. For clarity of discussion, the terms “cohesion” and “adhesion” will be used herein in accordance with this nomenclature.
Due to the cohesive bond created by the spreading of the pressure sensitive adhesive on the backs of the CD label and the center hole section, when the CD label is peeled from the label sheet the center hole section sometimes coheres strongly enough to the CD label so that the CD label pulls the center hole section with it from the liner. The user must then perform the separate step of removing the center hole section from the CD label after the CD label's sticky side is already exposed. This separate step can be awkward.
One method which has been suggested for preventing this cohesion problem and ensuring that the unneeded or waste section of the facestock remains on the liner when the label is peeled away, is by the use of skips. Skips are localized areas on the liner in which the release coating is modified, either by using a different release coating that constitutes a less effective non-stick agent, or by completely eliminating the release coating at the skip. The intended result is that the unneeded facestock section remains strongly adhered to the liner while the label is peeled away from the liner, leaving the unneeded section behind. Examples of label sheets or strips employing skips or other techniques that rely on differential bond strengths are U.S. Pat. Nos. 5,580,640; 6,273,987; 6,410,111; 6,423,391; and 6,432,499. One drawback to the conventional skip approach is that attempting to use different release coatings in different areas, or different thicknesses of the same release coating in different areas, complicates the manufacturing process. The labels sheets are usually made in large continuous rolls, and attempting to create local and repeated small areas in those rolls in which the release coating is different, then applying the facestock, and then aligning those small localized areas with the label patterns later die cut into the sheets, undesirably complicates the manufacturing.